Thermal fluctuation and collisional damping effects in the GDR observables in hot rotating 176W nuclei

The strength function and the angular distribution of the high energy γ-rays emitted by the giant dipole resonance (GDR) in hot rotating 176W nuclei have been measured at temperature T ≈ 1.4 MeV and at 4 values of the angular momentum I in the interval I = 35–55, ħ. The measured GDR width is found not to change when the angular momentum is varied. An increase by a factor of ≈ 2 is measured for the a2(Eγ) in the same I interval. The comparison of the data to model predictions shows that the collisional damping width is independent of temperature and rotational frequency and that thermal shape and orientation fluctuations are responsible for the measured widths and angular anisotropies.